This invention relates generally to a fuel filter for engines such as Diesel engines and more particularly to fuel filters having heating elements.
During winter operation of a vehicle, obstructions frequently occur in the vehicle engine fuel filter due to the formation of solid fuel matter caused by low temperatures. In order to avoid the danger of the occurrence of these obstructions in the fuel filter, filter designs incorporating heating units are known. One such design (see BMW Service Information, Structural Components: 13, Fuel Processing and Controlling, September 1983) discloses an electric heating element for heating fuel which is arranged between a filter head and a filter box. The heating element, which is disk-shaped and automatically controlled, is secured to a filter head along with a filter box by means of a central bolted connection. When it is necessary to change the filter box, the flow of fuel to the filter is interrupted and the filter box is detached from the threaded bolt that is firmly connected with the filter head. During this operation, the residual fuel located in the filter head and the heating element runs out and is discharged into the surrounding area in a downward direction.
One objective of the present invention is to provide a fuel filter device permitting quick and efficient change of an attached filter box.
Another object of the present invention is to provide a filter device which permits replacement of the filter box without discharge of residual fuel contained in the fuel filter into the surrounding area.
These and other objects of the present invention are achieved by the provision of a heated fuel filter for motor vehicle engines having a built-in device for preventing spillage of fuel contained in the filter element during replacement of the filter box portion of the filter. The heatable fuel filter comprises a heating element located between a filter head having an inlet and outlet duct and a filter box. The filter head, heating element and filter box are secured together at the filter head by a central bolted connection. When assembled, a portion of the heating element extends into the filter box, thereby occupying a portion of the interior of the filter box. When the filter box is removed from the filter head/heating element assembly, residual fuel contained in the filter head and heating element drains into the space in the filter box which was previously occupied by the lower portion of the heating element. Since the volume of this region (which, prior to disassembly, was occupied by the lower portion of the heating element) is designed to be greater than the volume of fuel contained the filter head and the heating element, fuel draining from the filter head and the heating element will be completely contained in this region without discharge of fuel into the surroundings. This will be true regardless of the fact that the filter box is filled to capacity while attached to the heating element after interruption of the fuel flow to the filter.
It is further contemplated that a sealing ring or gasket may be located in the upper portion of the filter box. In addition to performing a sealing function between the filter box and the heating element, this sealing ring may delimit part of the region of the filter box which receives the residual fuel draining from the filter head and heating element. A support for this sealing ring can be provided on the upper portion of the filter box. This support may comprise a holding plate formed by the cylindrical wall of the filter box along with a flat peripheral portion of the filter box adjacent the cylindrical wall.
In a further development, a central bolted connection securing the filter box to the filter head/heater element assembly comprises a fastening screw penetrating the filter head, heating element and a threaded hole in the filter box. In this manner, quick removal of the filter box becomes possible and spilling of fuel is avoided during the removal procedure.
A further advantageous development comprises flanging the heating element to the filter head by means of several fasteners. Preferably, three or more screws are employed. Such a construction precludes rotation for detaching of the heating element from the filter head when the filter box is removed. In this manner, the rotating or detaching problem of the prior art device described above is effectively overcome.
In another advantageous embodiment, fuel discharged from tne heating element is minimized by providing drainage means within the heating element which prevent fuel accumulation above a selected level.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.